Is it actually waterproof? Simba - Odyssey March 29, 2018 03:40 Updated Follow We've done our research and can confirm they are 100% waterproof - creating the perfect barrier from spills and stains. Related articles Is the protector hypoallergenic? Why should I choose a Simba Mattress Protector? How do I use my Simba Mattress Protector? What is the protector made of? Can you take away my old mattress?